Flexible electrical isolation device

ABSTRACT

An electrical isolator includes a flexible non-electrically conductive membrane and an inelastic flexible dielectric member journaled in the membrane and extending from the first end of the membrane to the second end of the membrane. First and second couplings are mounted to the ends of the dielectric member. The ends of the membrane are mated in sealed engagement with the couplings so as to fluidically seal the ends of the membrane and the dielectric member within the membrane. The membrane is filled with a dielectric fluid so as to displace any air in the membrane and the dielectric member. The couplings are adapted to couple to objects at opposite ends of the electrical isolator.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/246,747 filed on Jan. 14, 2019 entitled “Flexible ElectricalIsolation Device”. U.S. patent application Ser. No. 16/246,747 is acontinuation-in-part of U.S. patent application Ser. No. 15/879,691filed on Jan. 25, 2018 which in turn is a continuation of U.S. patentapplication Ser. No. 15/332,113 filed on Oct. 24, 2016, both alsoentitled “Flexible Electrical Isolation Device”. U.S. patent applicationSer. No. 15/332,113 is a continuation of U.S. patent application Ser.No. 14/664,724 filed on Mar. 20, 2015 also entitled “Flexible ElectricalIsolation Device”. U.S. patent application Ser. No. 14/664,724 is acontinuation-in-part of U.S. patent application Ser. No. 14/633,749filed on Feb. 27, 2015 entitled “Method For Stringing ReplacementOptical Ground Wire Or Static Wire Near Energized Power Lines” andclaims priority from U.S. Provisional Patent Application No. 61/968,543filed on Mar. 21, 2014 entitled “Flexible Isolation Device For WireStringing”. Entireties of all the applications identified in thissection are incorporated herein by reference.

TECHNICAL FIELD

This disclosure generally relates to a flexible electrical isolationdevice, one example of which is for use in replacing energized powerlines or in stringing replacement optical ground wire or static wirenear or above energized power lines.

BACKGROUND

There are many examples, some of which are provided herein, where theapplicant believes it to be beneficial to provide a tensile loadbearing, electrically insulating, flexible isolation member which isweather resistant. One example, already mentioned, is for use inreplacing, or what applicant refers to as reconductoring or restringingof power line conductors or static wires respectively. Other examplesmay include the use of the flexible isolation member in a sling lineunder a helicopter, for example when used to suspend a lineman from thehelicopter for power line maintenance work.

Overhead power lines may typically use one or more conductors, orphases, to transmit electricity within an electricity transmission grid.The overhead power lines may be used for bulk transmission ofelectricity from a power plant to centers of high demand and fordistribution within the centers of high demand. The conductors are oftensupported above the ground by support structures such as poles ortowers. Over time the energized transmission lines, referred to hereinas energized conductors, may be exposed to harsh weather conditions orbecome overloaded. Deteriorated or overloaded conductors are replaced byreconductoring.

Static wires may be strung above the conductors to shield the energizedconductors from lightning strikes. Occasionally the static wires, whichmay be conventional static wires or otherwise may be referred to asoverhead ground wire, shield wire, earth wire, etc., or which may beoptical ground wire (OPGW), collectively referred to herein as staticwire, must also be replaced in a process referred to as restringing.During the reconductoring or restringing process it is oftenadvantageous to use pulling wire instead of pulling rope because thepulling rope may burn, melt, heat-and-break or otherwise fail if moistand/or dirty when exposed to a high voltage environment. Also pullingtensions for transmission conductors is above rope rating. A highvoltage environment occurs when pulling conductors or static wirebecause each may be subjected to a significant induced voltage due toproximity to one or more high voltage energized conductors, for examplecarrying 69 kV or more. The use of pulling wire advantageouslynecessitates the use of a flexible, electrically isolating link betweenthe pulling wire and the conductor or static wire that is to bereplaced, so as to electrically insulate the conductive pulling wirefrom the energized, induced or potentially energized, conductor orstatic wire.

SUMMARY

Accordingly in one aspect, a method for assembling an isolation link isprovided. The method steps comprise mounting a flexible membrane havingopposite first and second ends around an elongate dielectric flexiblemember having a plurality of strands and first and second ends. Thefirst end of the flexible member protrudes from the first end of themembrane and the second end of the flexible member protrudes from thesecond end of the membrane. The method further comprises mounting afirst sealing assembly to the first end of the membrane and a secondsealing assembly to the second end of the membrane so as to fluidicallyseal the first and second ends of the membrane. The first and secondsealing assemblies' are adapted to couple to a corresponding socket.Each socket has a frustoconical bore, and each frustoconical bore has aninterior surface, a narrow opening and an opposite wide opening. Thenarrow openings of the sockets are adjacent their respective sealingassembly of said first and second sealing assemblies. Further, themethod comprises coupling the narrow end of the first socket to thefirst sealing assembly and the second socket to the second sealingassembly. Further, the first socket is mounted to the first end of theflexible member so that the flexible member extends into the bore of thefirst socket, and the second socket is mounted to the second end of theflexible member so that the flexible member extends into the bore of thesecond socket. The first and second ends of the flexible member arebroomed so as to form corresponding first and second broomed strands soas to expand the ends of the flexible member within the frustoconicalbores of the first and second sockets respectively. A liquid fixingagent is inserted into the first and second broomed strands and thefrustoconical bores of the first and second sockets, so as tosubstantially fill voids between the rope strands of the first andsecond broomed strands and between the first and second broomed strandsand the inner surface of the frustoconical bore, and so that the liquidfixing agent is substantially uniformly infiltrated into the narrow endsof the first and second sockets. The method further comprises curing theliquid fixing agent to secure the first and second broomed strandswithin the first and second frustoconical bores respectively, andmounting a first coupler to the wide end of the first socket and asecond coupler to the wide end of the second socket.

Accordingly, in another aspect, a method of assembling an isolationdevice for use in repair or replacement of energized power lines andcomponents associated therewith is provided. The method compriseslocating a first distal end portion of a dielectric rope in a firstsocket so that at least a length of the first distal end portion of therope resides within a frustoconical cavity of the first socket. Further,a non-porous, non-rigid tube is located over a length of the dielectricrope. The tube extends up to a first, narrow end of the first socketcavity. Further, at least a first distal end portion of the tube iscoupled to the first, narrow end of the first socket so as to make afluidic seal therebetween. The method further comprises using aliquid-to-solid resin setting to set the first distal end portion of therope within the first socket cavity so as to prevent movement of thefirst distal end portion of the rope within and along the longitudinalaxis of the first socket cavity. Further, the above-stated steps arerepeated for coupling and fluidically sealing at least a second distalend portion of the tube to a corresponding second socket and, aliquid-to-solid setting resin is used to set a second distal end portionof the rope within a frustoconical cavity of the second socket. The tubeis then filled with a dielectric fluid so as to displace any air in thetube and the dielectric rope.

Accordingly, in another aspect, an electrical isolation device isprovided. The device comprises a dielectric rope having first and secondopposed distal end portions and first and second sockets for receivingthe first and second opposed distal end portions of the rope withintheir respective socket cavities. Further, the device comprises anon-porous, non-rigid tube extending over a length of the dielectricrope. The tube extends at least up to an inner distal end of each of thefirst and second socket cavities. The device also comprises first andsecond couplers located at about the inner distal ends of the first andsecond socket cavities for coupling at least the first and second distalend portions of the tube to their respective first and second sockets.Leakage of a dielectric fluid contained within the tube is prevented bythe first and second couplers and resin setting of the first and seconddistal end portions of the rope within their respective cavities.

Accordingly, in another aspect, an electrical isolator is provided. Theisolator comprises an elongate flexible dielectric member encased in acorresponding length of flexible dielectric tubing filled withdielectric fluid. Opposite ends of the tubing and member are sealed toprovide a fluid seal.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is, in perspective view, a partly cut-away end view of an exampleof a flexible, electrically insulated, isolation link.

FIG. 2 is a side elevation view showing an isolation link passingthrough a sheave during pulling.

FIG. 3 is a partially cut away side elevation view of the isolation linkof FIG. 1.

FIG. 4 is a section view along line 4-4 in FIG. 3.

FIG. 4A is an enlarged view of a portion of the end of the isolationlink illustrated in FIG. 4.

FIG. 5 is, in perspective exploded view, the isolation link of FIG. 1.

FIG. 6 is, in side elevation view the isolation link of FIG. 5.

FIG. 7 is, in perspective view, the coupling of FIG. 6 with the flexiblemembrane removed to show the annular channel between the internal andexternal components of the hose fitting.

FIG. 8 is the coupling of FIG. 7 with the dielectric rope and externalcomponent of the hose fitting removed.

FIG. 9 is the coupling of FIG. 8 in opposite perspective view.

FIG. 10 is the coupling of FIG. 8 with internal component of the hosefitting removed to expose the seal face of the socket and the sealingo-ring.

DETAILED DESCRIPTION

With reference to the FIGS. 1-10, wherein like parts in each view aredenoted by corresponding part numbers, isolation link 10 is a flexible,weather resistant and preferably weather-proof, electrical insulatorhaving at least the following properties: a) it does not conductelectric current; and b) it will bear a tensile load of, for example,30,000 to 50,000 lbs. depending on the particular embodiment. In oneembodiment, not intended to be limiting, isolation link 10 includes aswivel to allow for swiveling, rotation, or other relative movementalong the link 10 of one portion of the link relative to another, so asto relieve torque loading on or at the end of the link due to any torqueapplied to the link from, for example, a pulling wire or a pulling rope.In other embodiments the swivel may be a conventional, separatecomponent. Isolation link 10 may be a length, for example twelve feetlong of tensile and dielectrically tested insulated rope havingdielectric properties, protected or shielded from the weather or otheradverse elements that may compromise the rope's dielectric properties.The protection or shielding will protect the entire length of insulatedrope and may for example take the form of a hose, tube, membrane or likecontinuous, fluid impermeable, cover or shield.

In the reconductoring or restringing application, isolation link 10electrically isolates between a pulling wire 12 (and the associatedworkers and the stringing equipment) and the to-be-replaced conductor orstatic wire 14 as the pulling wire 12 is strung through the power linesystem, for example so as to continuously travel in direction A in anuninterrupted motion over one or more sheaves 16.

A description, at least in part, of the isolation link is provided inUnited States patent application publication no. US 2015/0270035,published on Sep. 24, 2015, entitled Flexible Electrical IsolationDevice, and in applicant's United States patent application publicationno. US 2015/0249325, published on Sep. 3, 2015 entitled StringingProcedure to Replace Existing Static Line with OPGW, which are includedherein in their entirety by reference.

As described above, isolation link 10 provides, in one embodiment notintended to be limiting, an electrically insulated connection between anold conductor or static wire 14 (e.g. the old conductor or static wireto be replaced) and the pulling wire 12 so as to break an electricalcircuit. An example of such an electrical circuit that may beencountered on an energized reconductoring project is referred to as a“circulating current,” induced in the de-energized, old conductor beingreplaced, due to the proximity of the de-energized old conductor to oneor more nearby energized conductors. The circulating current maycomplete or close the circuit by running through the earth underneaththe conductors.

Thus, although the replacement or new conductor wire being installedduring the reconductoring is not directly energized by a powergenerating station, the proximity of energized conductors or phasescreates an energized environment which may impart an induced voltage andcurrent in the pulling wire and in the new conductor wire. Runninggrounds are used at each end of the pull, (puller and payout) in orderto protect the equipment and the workers who are required to be in closeproximity to the wires. However, multiple running grounds, combined withthe induced voltage and current, may result in a circulating currentwith unknown and unpredictable electrical forces. Hence it is desirableto use an isolator link 10.

Although during reconductoring or restringing, a non-electricallyconductive pulling rope may be employed during periods of what isarguably considered to be “good weather” instead of an electricallyconductive pulling wire, it is in applicant's opinion prudent to use anisolation link in accordance with the present teachings in thosesituations also, in case of inadvertent deterioration of the pullingrope's dielectric properties due to electrically conductive moisture,dirt, oil or other contamination, which may or may not be evident to anobserver. Applicant has found that high voltage levels in the energizedconductors, which have been found to induce a voltage and current inproximately located non-energized conductors or static wires, whencombined with the adverse effect on the dielectric properties of apulling rope due to moisture and/or dirt, etc. in or on the pullingrope, may cause the pulling rope to melt and break or otherwise fail.Use of dielectric tested isolation rope installed between the pullingline and the new wire can be used to isolate or separate the runninggrounds, however the rope itself poses a safety hazard due to thepotential for the rope to become contaminated by dirt, oils, airborneparticles, high humidity, or precipitation rendering the rope at leastsemi-conductive thereby eliminating the amount of effective isolationbetween the pulling line and the new wire, and therefore making theisolation rope weather-proof is an improvement. Improving the dielectricproperties of the rope is a further improvement.

Thus, as will now be understood, elimination of the circulating currentwhile providing electrical protection on both ends of the pull may beaccomplished by electrically isolating the pulling line or pulling wirefrom the new wire by using an isolation link 10. This allows theinstallation of running grounds on both ends of the pull with a reduceddanger of creating a circulating current.

In one embodiment, a length of dielectric rope 18 is encased in aflexible, preferably non-tensile-load bearing, dielectric membrane 20.The membrane 20 is filled with dielectric oil 22 or other inertdielectric fluid so as to soak, completely bath and/or surround eachindividual fibre or strand 18 a of the dielectric rope 18, andcompletely impregnate the dielectric rope 18 to thus exclude air in theinterstices between the fibres 18 a of the dielectric rope 18 and in anyvoids between the rope 18 and the flexible, dielectric membrane 20. Thelength of the isolation link 10 depends on the required electricalinsulation, as would be known to one skilled in the art. Typical lengthsfor isolation link 10 may be in the range of approximately 8-20 feet forhigh voltage transmission reconductoring (e.g. in the range of 69 kV to345 kV or greater), or, for example, in the range of 50-250 feet forslinging a load such as a lineman under a helicopter.

Each end of the isolation link 10 is fluidly sealed to maintain the oil22 or other dielectric fluid in the membrane 20 and in the rope 18, andnot leak outside the membrane 20, even under a maximum tensile load ofthe dielectric rope 18 employed within the membrane 20.

In the applicant's experience, typical tensile loads acting on theisolator link 10 positioned between a pulling wire and a conductorduring a reconductoring may be 5,000 lbs. but sometimes approachapproximately 12,000 lbs. to 15,000 lbs. Thus, depending on the diameterof rope 18, as a precaution, the isolation link 10 advantageously shouldbe capable of bearing tensile loads along the order of 50,000 lbs. for,for example, ¾ inch diameter rope, so that the isolation link 10 maybear tensile loads of approximately three to four times the typicalmaximum tensile loads under which the isolation link 10 would be placedduring a reconductoring project. It has been found that ¾ inch rope 18when mounted at its end 18 a into socket cavity 28 a, could withstand atensile force in direction C in the order of less than or equal to50,000 lbs. when socket cavity angle □ was 13.6 degrees and the methoddescribed herein was followed.

Thus isolating insulator link or isolation link 10 may be characterizedin one aspect as including a flexible elongated tensionally-stronginsulating member, such as a dielectric synthetic rope (hereincollectively referred to as a flexible member), which is encased in aweather-proof flexible sleeve, hose, tube, or enclosing membrane (hereincollectively referred to as a flexible membrane), wherein terminatingcouplings are mounted at either end of the generally co-terminusflexible member and flexible membrane. The terminating couplings may inone embodiment provide for relative torsion relief and relative bendingmoment relief between, respectively, for example the pulling line at oneend of the isolation link and the new wire at the other end of theisolation link. Optionally, in one embodiment the couplings at eitherend of the elongated isolation link each include a first joint allowingrelative bi-directional movement between two portions, for example twohalves, of the coupling. A second joint may be provided allowingrelative rotation or swiveling about a longitudinal axis of thecoupling. The first joint may for example be a universal joint, or aball joint, or a tensionally strong flexible stem encased within thecoupling. The second joint may for example be a swivel. A single jointmay be provided to replace the function of both the first and secondjoints. Alternatively no swivel or flex joint is provided in theterminating coupling; in which case a separate swivel known in the artmay be employed.

As stated above, one example of the flexible dielectric member inisolation link 10 proposed by the applicant uses a length of dielectricrope which is encased in a flexible membrane, wherein the flexiblemembrane is filled with dielectric fluid, for example silicon oil, so asto impregnate the dielectric rope and exclude air in the interstices orvoids between the fibres of the rope and in any voids between the ropeand the walls of the membrane. Suitable silicon oil may be STO-50™silicone Transformer Oil (100% polydimethylsiloxane) sold by ClearcoProducts Co., Inc. of Willow Grove, Pa., USA. A suitable dielectricfluid 22 may have a viscosity of about 0.5 centi-stoke. Each end of theisolation link is sealed to maintain the dielectric fluid within themembrane and rope, and to keep air and moisture out. The seal or sealingassembly may be provided in a terminating coupling where the ends of theflexible membrane mount to the terminating couplings. In someembodiments, the dielectric fluid may be a high-contrast color ascompared to the color of the exterior surface of the membrane and thecouplings, so as to enable better visual detection of the dielectricfluid in the event any leaking of the dielectric fluid from theisolation link 10 should ever occur.

The flexible member is flexible or bendable or otherwise substantiallynon-resiliently deformable while resisting lengthening due to tensileloading (herein, collectively referred to as flexible) to accommodatefor example the bending radius of a traveler, sheave, or dolly (sheave16 as used herein). In one example the flexible member is composed of aflexible, high tensile strength, dielectric material such as ropestrands 18 b twisted and/or braided into a dielectric rope 18. Theisolation link 10, when properly maintained, is advantageouslyimpervious to air, moisture, dirt, oils and airborne particles includingdust, thereby mitigating the potential for the isolation link, and inparticular the flexible member portion of the isolation link, becomingelectrically conductive during use.

As stated above, flexible member may, for example, be a synthetic rope18 constructed of a plurality of strands or fibers (collectively hereinreferred to as strands 18 b) that may be twisted and/or braided togetherto form the rope 18. The plurality of strands may be manufactured of avariety of dielectric materials. By way of example, without intending tobe limiting, the applicant has found that the dielectric flexible membermay be made of a dielectric rope sold under the trademark Plasma® 12Strand by Cortland Company. Such a dielectric rope, for example, mayhave a % inch diameter. Other examples of the flexible member mayinclude ultra-high molecular weight polyethylene (an example of whichincludes the synthetic ropes sold under the trademark AmSteel® Blue),high modulus polyethylene, aromatic polyamides (otherwise referred to asaramids), para-aramids (an example of which includes the material soldunder the trademark Kevlar®), aliphatic or semi-aromatic polyamides (anexample of which includes the material sold under the trademark Nylon™),and any other flexible, high tensile strength substantiallynon-resilient, dielectric materials suitable for constructing anisolation link as described herein that would be known or will becomeknown to a person skilled in the art, such as for example a ropeengineer.

The flexible membrane encasing the flexible member is also constructedof dielectric material(s) and may include, for example, a rubber tube orhose suitable for hydraulic fluid applications. Although the flexiblemembrane may be in the form of a hollow tube or hose, it will beappreciated by a person skilled in the art that the membrane may alsoinclude, for example, a sheet of material that is formed, for example,as a sleeve around the flexible member so as to create a sealed membraneencasing the length of the flexible member, or any other method formanufacturing a sealed membrane around a flexible member as would beknown or will become known to a person skilled in the art. Optionally,the flexible membrane may be wholly or partially constructed of clear,translucent, or transparent materials (for example if the membrane is atube having an inspection window strip along its length), so as tofacilitate inspection of the dielectric member within the isolation linkfor degradation or for the presence of air within the sealed membrane orother indications of the state of the components of the isolationmember. The flexible membrane may also be reinforced, for example asfound in conventional insulated air or hydraulic hoses. The flexiblemembrane may be sold under the trademark Gorilla® Multi-PurposeIndustrial Hose sold by Continental Conti-tech™ and may have an outerdiameter of approximately 1¾ inches and an inside diameter greater thanthe diameter of rope 18. The hose may have an external cover layer andan inner layer. The inner layer may be constructed of a nitrilesynthetic rubber. The external cover layer may be constructed of yellowsynthetic rubber, and reinforced with a spiral aramid yarn sold underthe trademark Carbryn®.

Isolation link 10 includes attachment couplings 24 at either end of alength of a flexible member 18. The couplings 24 themselves are not, atleast need not be, constructed of dielectric material and may forexample be made of stainless steel. The flexible member 18 is ofsufficient length to provide electrical isolation for the rated systemvoltage to which dielectric flexible isolation link 10 will be exposedwithout the need for the connection joints or couplings 24 to bedielectric. In the application, without intending to be limiting, of theisolation link 10 being used in a wire replacement procedure, couplings24 attach isolation link 10 to the pulling wire 12 at a first coupling24, and to the new or old conductor 14 at a second coupling 12, wherethe first and second couplings 12 are at opposite ends of isolation link10.

Coupling 24 may include an eye 32 a for attaching to the end of aconductor 14 or pulling wire 12.

As described above, flexible member 18 in one embodiment includes asynthetic dielectric rope encased in a flexible membrane 20, bothmounted at each end thereof to a corresponding coupling 24. Thedielectric rope is snugly shrouded in a flexible membrane 20, which inone embodiment is flexible tubing. The tubing is slightly shorter thanthe length of the rope so as to expose the end 18 a of the rope 18 as itprotrudes from both ends 20 a of the tubing 20.

Each coupling 24 includes a socket 28. Socket 28 is hollow along axis B.A conical cavity 28 a is formed in socket 28. As best seen in FIG. 4A,the end 18 a of rope 18 is exposed beyond the end 20 a of flexiblemembrane 20 and inserted through hose fitting 30 so as to protrude intocavity 28 a. The individual strands 18 b of rope end 18 a are separatedso as to substantially fill cavity 28 a as cavity 28 a opens from itsnarrow end or neck 28 b to its wide end 28 c. Socket 28 may besubstantially cylindrical along its external surface corresponding tothe length of cavity 28 a.

A cap 32 having an eye 32 a may be mounted, as by threading, onto theend of socket 28 corresponding to the wide end 28 c of cavity 28 a. Hosefitting 30 is mounted to the end of socket 28 corresponding to the neck28 b of cavity 28 a. Without intending to be limiting, hose fitting 30may include an internal component 30 a and an external component 30 b.Internal component 30 a threadably mounts into the female receiver 28 dof socket 28 so as to abut against an annular seal face 34 at, andperpendicular to, the opening into neck 28 b. An O-ring 36 is compressedbetween base 38 a of internal component 30 a of hose fitting 30 and sealface 34 of socket 28. External component 30 b of hose fitting 30threadably mounts onto the pipe end 38 b of internal component 30 a soas to define an annular channel 40. End 20 a of flexible membrane 20 isheld in channel 40, clamped between pipe end 38 b and the cylindricalwall of external component 30 b, held by threads 30 c on the cylindricalinner wall surface of external component 30 b. Internal portion 30 a ofhose filling 30 threads into engagement in female receiver 28 d ofsocket 28.

With the strands 18 b of rope 18 separated so as to substantially fillcavity 28 a of socket 28, resin, such as epoxy two-part liquid-to-solidsetting resin 42 is poured into cavity 28 a and infiltrated between theseparated strands 18 b, preferably so as to exclude any air from betweenstrands 18 b from end 28 c to neck 28 b of cavity 28 a. The resin 42 isallowed to set and fully cure.

Although not wishing to be held to any particular theory, it ispostulated by applicant that the maximum amount of the tensile load thatmay be applied in direction C to rope 18, and hence to strands 18 b ofend 18 a of rope 18 held in the solidified resin 42 in cavity 28 a maybe governed at least in part, by not only the size or diameter of therope 18 (the larger the diameter, the greater maximum tensile load), butalso by the uniformity of the dispersion of resin 42 throughout strands18 b, in particular in neck 28 b, and/or where the fluid resin 42intrudes non-uniformly along rope 18 in the area of neck 28 b, forexample unevenly intrudes past seal face 34 into the bore base 38 a.Non-uniformity of dispersion or intrusion of fluid resin 42 may reducethe maximum loading capacity for rope 18.

Socket 28 has an oil passageway 44 sealed by a threaded set screw plug46. Oil passageway 44 may be linear, and connects a fill port 44 aformed in the side of socket 28 with an oil outlet at the seal face 34.The oil outlet aligns with a conically-shaped or flared opening intobore 38 c in base 38 a so that oil passageway 44 fluidicallycommunicates along pipe fitting end 38 b for the pressurized filling ofdielectric fluid 22 into rope 18 and into the spaces between rope 18 andflexible membrane 20 along the entire length of both rope 18 andflexible membrane 20 so as to not have air bubbles or air pockets withinmembrane 20 or rope 18.

Thus a tension load on isolation link 10 in direction C, alonglongitudinal axis B, is to be taken up substantially entirely by rope 18acting on socket 28, and not to a significant degree by flexiblemembrane 20. In a preferred embodiment, substantially no tensile load isimparted to flexible membrane 20; however, to the extent that anytension load is imparted, the threading 30 c on the interior of externalcomponent 30 b provides additional frictional engagement to the clampingof flexible membrane 20 provided between female receiver 28 d of socket28 and pipe fitting end 38 b.

As described above, dielectric rope 18 is typically comprised of aplurality of strands which are for example twisted or braided togetherto form the rope. During assembly of isolation link 10, the rope 18,constructed of a dielectric material such as those described above, isjournaled through the flexible membrane 20 with each end of the rope 18extending beyond the respective ends of flexible member 20. Next, asealing assembly, which for example may include socket 28 and hosefitting 30, is mounted to each end of flexible membrane 20 and rope 18so as to transfer tensile loading on socket 28 to only rope 18 and toseal in the dielectric fluid 22 within membrane 20 even under loading ofrope 18.

When the plurality of strands 18 b of each rope end 18 a are separatedthey may also be brushed, in a procedure referred to as “brooming,” soas to outwardly flare the rope end 18 a towards the wide end 28 c ofcavity 28 a while singulating the rope strands 18 b.

The liquid fixing agent referred to above as resin 42, may be, an epoxyresin and hardener mixture, prepared by mixing the resin and hardenertogether (the mixture) so as to avoid or reduce the creation of airbubbles, such as by using an electric stirring machine on a low speedsetting, or stirring the mixture slowly by hand. The epoxy resin andhardener mixture is then carefully poured or injected into the socketcavity 28 a to direct the flow of the mixture from the wide end 28 ctowards the neck 28 b of the cavity 28 a and towards the center of thebroomed rope end 18 a, so as to substantially completely fill the entiresocket cavity 28 a with the epoxy resin mixture without spaces or airpockets within the cavity 28 a and provide for substantially completepenetration of the rope strands within the cavity 28 a.

In some embodiments, advantageously for use in the aforesaidreconductoring or stringing procedure, the applicant has found that thesize and angle of the frusto-conical socket cavity 28 a and the diameterand density of the rope 18 may be selected such that a ratio of thevolume of the mixture of resin 42 to the volume of the rope strands 18 bwithin the cavity 28 a is substantially in the range of 1.5 to 2. Inother words, the ratio of the Volume_((mixture)):Volume_((rope strands))is in the range of substantially 1.5:1 to 2:1. Other ratios may alsowork, such as 3:1 or 4:1. An example of a suitable resin 42 forassembling the isolation link 10, in the applicant's experience,includes the #105 Epoxy Resin and #205 Hardener supplied by West System.However, this example is not intended to be limiting and it will beappreciated by a person skilled in the art that other suitable liquidfixing agents may be used and come within the scope of the presentdisclosure.

Once the resin 42 has cured, at this stage of the assembly a tensileload may be applied to the rope 18 encased within the membrane 20 so asto settle the cured resin 42 within the socket 28. It has been foundthat the cured resin may settle by a small amount, for example 1/16-⅛inch (1.6 mm-3.2 mm) upon tensioning.

It has been found that if the flexible membrane 20 is resilient alongits length, such as been found to be the case using Gorilla™ tubingreferred to above, then pre-tensioning of rope 18 is not required. Ithas been found that a small tensile loading on Gorilla™ tubing merelycauses a stretch in the tubing without pulling the tubing from the hosefittings 30 on couplings 24 or causing a leak of dielectric fluid 22.

Due to the frusto-conical geometry of the socket cavity 28 a, thehardened epoxy resin 42 forms a frusto-conical plug of substantially thesame geometry of the cavity 28 a. Thus, when a tensile force is appliedto rope 18 in direction C, the rope end 18 a, because it is embeddedwithin the epoxy resin solid plug, remains within the socket 28. Forexample, without intending to be limiting, the applicant found thatduring experimental testing a prototype isolation link 10 having ¾ inchdiameter rope 18 withstood pulling forces in the order of 50,000 poundsand the epoxy resin plug and rope end 18 a remained seated within cavity28 a.

As stated above, the frusto-conical geometry of the socket cavity 28 amay have an angle α measured from centroidal axis B of substantially13.6°. Where link 10 is for use in reconductoring or stringing, thediameter of the coupling 24 is constrained by the opening size in theannular channel of the pulleys or sheaves 16. Thus the angle □ and wallthickness of socket 28, which dictate the width and length of thecouplings 24 are optimized to most smoothly pass the couplings 24through the sheave channels of sheaves 16. For example, an optimummaximum diameter for a coupler 24 may be approximately between 1.5 and 2inches, which, given an overall length of the coupling 24 of for examplesubstantially eight inches (including hosefitting 30, socket 28 and cap32), constrains the angle □ to allow sufficient wall thickness towithstand the applied tensile force.

While the above describes certain examples of the present disclosure,various modifications to the described examples will also be apparent tothose skilled in the art. The scope of the claims should not be limitedby the examples provided above; rather, the scope of the claims shouldbe given the broadest interpretation that is consistent with thedisclosure as a whole.

What is claimed is:
 1. An electrical isolation link comprising: anelectrically insulating rope encased in the hollow cavity of a flexibledielectric fluid-impermeable weather shielding covering the rope so asto extend along substantially an entire length of the rope between theopposite ends of the rope, a dielectric fluid also encased within theweather shielding, wherein air in interstices between fibers of therope, air bubbles, air pockets, and air in voids between the rope andthe weather shielding are excluded by the presence of the dielectricfluid in the hollow cavity and impregnation of the dielectric fluid intothe rope, and wherein the opposite ends of the rope, and correspondingopposite ends of the weather shielding are sealed to form oppositefluidically sealed ends, and wherein each of the sealed ends are mountedto terminating couplings, wherein the rope is mounted to the terminatingcouplings to take-up substantially an entire tensile load applied to theterminating couplings, and wherein the terminating couplings are adaptedto couple to objects at opposite ends of the link, and wherein theobjects are chosen from the group consisting of: a pulling line, areplacement conductor, a to-be-replaced conductor, a new replacementconductor, a static wire, a slung load, an aerial vehicle.
 2. The linkof claim 1, wherein the terminating couplings further each include atleast one joint.
 3. The link of claim 2, wherein the at least one jointprovides for bending of the terminating couplings.
 4. The link of claim2, wherein the at least one joint provides for swiveling rotation of theterminating couplings.
 5. The link of claim 1, wherein the weathershield includes a clear membrane to provide for inspection by a userinto the hollow cavity.
 6. The link of claim 5, wherein the clearmembrane is a window strip.
 7. The link of claim 1, wherein the aerialvehicle is a helicopter and the slung load is a lineman slung beneaththe helicopter.
 8. The link of claim 1, wherein the rope fibers arechosen from the group consisting of: polymer, aramid, composite,synthetic.
 9. The link of claim 1, wherein the weather shielding istubing.
 10. The link of claim 9, wherein the length of the tubing isless than the length of the rope so that the opposite ends of the ropeprotrude from the opposite ends of the tubing so as to cooperate withthe terminating couplings.
 11. The link of claim 10, wherein theterminating couplings each include a coupling cavity and wherein theopposite ends of the rope extend into the coupling cavity and aremounted therein to the corresponding terminating coupling.
 12. Theapparatus of claim 11, wherein the coupling cavity is frusto-conical.13. The link of claim 11, wherein the coupling cavity is a socket andwherein each of the ends of the rope are flared within theircorresponding socket so as to substantially fill the socket and securedtherein by a liquid-to-solid setting compound.
 14. The apparatus ofclaim 13, wherein the socket is frusto-conical.
 15. The link of claim 1,wherein the dielectric fluid has been allowed to soak into the rope toexclude the air, air bubbles and air pockets.
 16. An electrical isolatorcomprising: an elongate flexible dielectric member encased in acorresponding length of flexible dielectric tubing adapted to be filledwith a dielectric fluid so as to substantially displace any air in saidmember and said tubing, and wherein the opposite ends of the tubing andmember are sealable to provide a fluid seal.
 17. The isolator of claim16, wherein the opposite ends are sealable by couplers and wherein themember and the tubing at either end are mounted to their correspondingcoupler, and wherein the member takes up substantially an entire tensileload applied to the opposite ends.
 18. The isolator of claim 16, whereinthe tubing is filled with the dielectric fluid.
 19. An apparatuscomprising: a dielectric elongate flexible membrane defining a hollowcavity, a first end, and a second end, wherein the hollow cavity isaccessible from each of the first end and the second end of the flexiblemembrane and is adapted to be filled with a dielectric fluid so as tosubstantially displace any air in at least said flexible membrane; and afirst coupling located at the first end of the flexible membrane, and asecond coupling located at the second end of the flexible membrane,wherein an interface between the flexible membrane at the first end ofthe flexible membrane and the first coupling, and the second end of theflexible membrane and the second coupling, are both fluidly sealed. 20.The apparatus of claim 19, further comprising: a dielectric rope locatedwithin the hollow cavity.
 21. The apparatus of claim 20, wherein thedielectric fluid is located within the hollow cavity.
 22. The apparatusof claim 21, wherein the dielectric fluid is located within intersticesof the dielectric rope.
 23. The apparatus of claim 21, wherein thedielectric fluid surrounds the dielectric rope.
 24. The apparatus ofclaim 19, further comprising: a dielectric rope located within thehollow cavity; and a joint in the first coupling.
 25. The apparatus ofclaim 24, wherein the joint is a swivel.
 26. The apparatus of claim 25,wherein the joint permits bending.
 27. The apparatus of claim 19,wherein the rope is connected to the first coupling and the secondcoupling.